Task: the structural floor required an upgrade from a live load capacity of 100 PSF (pounds per square feet) to new load of 25 PSF of super-imposed dead load and 150 PSF of live load.
Structure Details: Floor of the structure consists of a one-way cast-in-place slab on precast pre-stressed joist system, simply supported on continuous cast-in-place concrete beams with precast pre-stressed soffits running between columns of the structure.
Our Approach: Rapid Load Testing has been used to evaluate the in-place strength of the loose floor components and to develop an optimized and economical strengthening solution. On the basis of load test, we concluded that slab was strengthened enough to bear up new loads but the joist should be rated to 125 PSF of live load and the beam for 135, all greater than the theoretical load.
An externally bonded carbon FRP strengthening system was recommended consisting of multiple plies of FRP strips attached to joists soffit to increase the positive bending moment capacity and additional FRP strips were wrapped around the joists at each end to anchor the FRP strips. The beams were strengthened to improve their positive and negative moment capacity by installing FRP strips the soffit of the beam for positive moment and on top of the slab for negative moment. On top of the slab, the required amount of FRP for beam upgrade was equally divided and installed of each side of the column in the direction of the beam.
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